Definitely possible.
I used to be an avid MMO player throughout High School and College (Everquest, Anarchy Online, Final Fantasy XI, XIV ARR, World of Warcraft, Rift, Star Wars: The Old Republic, Dungeon Fighter Online, and many more I can't even remember right now)
Everquest and SW:TOR were the only ones I made a decent profit on, although that was never the goal. I was always just happy to make back the money that I spent on the game + subscription while having hundreds of hours of essentially free fun.
I'd argue that professional eSports is never the way to go unless you're an extreme outlier. (That's similar to saying to someone oh if you want to make money with football just go join the NFL) I believe the DOTA2 world championships or something was recent and the team who won split a $6,000,000 pot.
RMT of either in-game currency, items, characters, or powerleveling services is best if you're not comfortable in front of a camera or Twitch / Youtube if you think you have a good personality, a niche, and can entertain and grow a fanbase.